Major league pitcher Juan Guzman has been knocked out of the lineup repeatedly during the past four years by injuries to the right arm. (Reuters)

By Don Colburn
Washington Post Staff Writer
Tuesday, April 6, 1999; Page Z12

When future Hall of Famer Roger "The Rocket" Clemens fires a baseball toward home plate, he unleashes an awesome force.

To opposing batters, it's a virtually unhittable 95 mph fastball.

To athletic trainers and orthopedists, it's a feat of "biomechanics" – the windup, leg kick, delivery and follow-through that have enabled Clemens to throw that fastball past major league hitters for 15 seasons.

"Throwing a baseball is not a natural act," said Benjamin S. Shaffer, director of sports medicine at Georgetown University Medical Center and team doctor for the Georgetown Hoyas basketball team. "Throwing it with intensity and speed and control is absolutely an acquired skill."

Pitching requires a complex, twisting motion that transfers energy from the feet through the legs, hips and torso to the arm – and finally to the ball. Enormous rotational forces impinge on the shoulder and elbow.

	As shown in this skeletal model, pitching a baseball generates huge forces that can stress the shoulder and elbow. (Johns Hopkins University)

"Essentially, when you throw a ball, the resulting force is trying to pull your arm off your body," said Edward G. McFarland, director of sports medicine and shoulder surgery at Johns Hopkins Medical Institutions in Baltimore. "It's like somebody is trying to dislocate your shoulder."

In a three-year study of college baseball players, McFarland found that arm injuries accounted for three-quarters of the time out of the lineup. Tendinitis of the shoulder was the most common injury. Infielders underwent arm surgery as often as pitchers – perhaps because they must throw at a variety of angles, often off-balance.

"The shoulder wasn't really designed to pitch a baseball," McFarland said. "If you throw long enough, you're going to have shoulder problems. Look at why guys [have to] leave the major leagues. Some of them don't have the talent, but others just wear out."

Because baseball is more a skill game than a contact sport, traumatic and disabling injuries are rare. One study of Little Leaguers found that fewer than 2 percent were seriously injured during a season. At the high school level, injuries knock players out of the lineup less often in baseball than in football, soccer or basketball.

But lesser injuries such as minor sprains and muscle pulls are common in baseball. And so are sore arms.

'Shin Splints in Your Shoulder'

Protecting a Young Ballplayer's Arm

Warm up gradually; cold or tight muscles are easily strained. Begin with short, easy tosses – from 10 or 15 feet – before throwing hard. Don't overdo it during the first few days of spring practice – or the first few minutes of any practice. Pitching involves more than the arm. Keep the rest of the body in shape with running, biking, swimming, situps, stretches. Avoid a sidearm delivery, which puts more stress on the elbow than an overhand motion. The same goes for the curve ball. Pay attention to any pain. If your arm hurts, tell your coach. Coaches should never ask a player to "play through" pain in the arm.

Pitching is especially strenuous on a young arm that is still growing.

"Children are not little adults," Georgetown's Shaffer said. "They are at risk of injuries in ways that adults are not."

In adults, the strain is mainly on the tendons, muscles and ligaments that hold a joint together. For children, there's an additional risk, because their bones and joints are still developing.

Children grow from the ends of their bones, not the middle. So-called growth plates at the ends of the long bones are what Shaffer calls "the weak link of the musculoskeletal system in kids." Their cartilage – the smooth, shiny gristle like that on a chicken drumstick – is softer than that of adults.

Growth plates and soft cartilage are vulnerable to repetitive stress – for example, from throwing a baseball 100 times a day. If a young player ignores pain in the arm, the growth plates can stretch or crack. This happens most often on the inside of the elbow, where fragments of bone can even break off.

"When you put a lot of stress on the shoulder or elbow, the thing that gives first is the growth plate," McFarland said.

The two most common overuse injuries in young ballplayers are dubbed "Little League elbow" and "Little League shoulder." Both are catch-all terms, like "low back pain."

Little League shoulder is an injury to the growth plate in the humerus, the upper arm bone. The knobby upper end of the humerus is the ball in the ball-and-socket shoulder joint.

"Basically, it's a stress fracture of the humerus," Shaffer said. "That growth plate acts almost like taffy and pulls apart. It's like having shin splints in your shoulder."

In theory, a weakened growth plate could eventually break, like a wire coat hanger that snaps if it is bent back and forth often enough. But rest almost always gives it a chance to recover.

The main symptom is pain or tenderness in the shoulder. The damage may not show up on an X-ray – which is why arm soreness is such an important signal.

"Pain in the throwing arm of a kid is not normal," McFarland said.

Little League elbow, more common than Little League shoulder, is a repetitive-stress injury to the growth plate or the cartilage of the elbow. When a pitcher cocks his arm behind his head and snaps it forward, tremendous stress concentrates on the elbow.

'No pain, no gain is not a reasonable principle when it comes to throwing. A parent or coach can ruin a kid's elbow by forcing him to throw through the pain.'

- Benjamin S. Shaffer, director of sports medicine at Georgetown University Medical Center

Two studies of Little Leaguers, in Houston and in Eugene, Ore., found that about one out of five pitchers under age 13 experiences significant elbow pain during the season. The pain is more common on the inner side of the joint. ("Tennis elbow" usually strikes the outer side of the joint.)

Throwing a curveball puts even more stress on growth plates by "torquing" the elbow. But while Little League elbow once was thought to be caused by throwing curveballs, it is now known to result mainly from sheer wear-and-tear.

"The number one reason for problems is overuse – too much throwing," said William Grana, an orthopedic surgeon in Oklahoma City who is chairman of the sports medicine committee of the American Academy of Orthopaedic Surgeons.

And "throwing like a girl" has nothing to do with it. "That's baloney," Grana said. "I don't think there's any difference. Girls throw just like boys and are subject to the same types of injury."

Studies show that before age 13, when boys start to gain an advantage in muscle mass, there's no physiological reason for boys and girls to throw differently. When young boys and girls are asked to throw a ball with their nondominant arm – right-handers throwing with the left, and vice versa – girls throw just as accurately and far as the boys. In other words, the reason young boys tend to throw better than young girls with their dominant arm is that they have had more practice, and more coaching.

On the Disabled List
As with Little League shoulder, most cases of Little League elbow heal if the player takes a break from throwing. Continuing to throw with a painful elbow could cause permanent damage to the bone or cartilage – an injury called osteochondritis.

"'No pain, no gain' is not a reasonable principle when it comes to throwing," Shaffer said. "A parent or coach can ruin a kid's elbow by forcing him to throw through the pain."

'Essentially, when you throw a ball, the resulting force is trying to pull your arm out of your body. It's like somebody is trying to dislocate your shoulder.'

- Edward G. McFarland, director of sports medicine and shoulder surgery, Johns Hopkins Medical Institutions

Thomas J. Gill, an orthopedist at Massachusetts General Hospital, noted that some high school players work out or play all year, never giving their arms an offseason rest. They need to stop throwing for a while, he said. Usually rest and cross-training – substitution of a different sport or exercise, such as bicycling or swimming – will relieve the arm pain.

Another way to control the stress on the shoulder and elbow is to limit the number of pitches thrown. Little League Baseball rules limit 12-year-old pitchers to six innings a week and 13-to-16-year-olds to nine innings a week. The youngest Little Leaguers don't pitch at all: Batters hit the ball off a waist-high tee or swing against pitches thrown by a machine or an adult.

Coaches sometimes also impose pitch counts to limit the strain on a youngster's arm. According to the American Academy of Orthopaedic Surgeons, "a reasonable approach is to count the number of pitches thrown and use 80 to 100 pitches as a maximum in a game, and 30 to 40 pitches in a practice."

Even professional teams set pitch limits. Grana, who is also team physician for the Oklahoma RedHawks, the AAA minor league team for the Texas Rangers, said the team's pitchers are limited to six innings, or 120 pitches per game.

"We want those guys to use their arms in the big leagues," Grana said.

A major league starting pitcher typically pitches every fifth day and may not throw hard at all between starts. "In effect, he injures his arm," said Stephen G. Rice, a sports medicine specialist at the Jersey Shore Medical Center in Neptune, N.J., "and we nurse his arm back to health by the fifth day."

Taking care of major league pitching arms has become a highly sophisticated biomedical science. Radar guns track the velocity of their pitches, computer models chart their pitch location, and coaches scrutinize their "mechanics," looking for the slightest change of motion that might be a sign of fatigue or injury.

As the 1999 season opened yesterday, 25 pitchers were on the Disabled List because of arm injuries, including Kerry Wood of the Chicago Cubs, Andy Pettitte of the New York Yankees, Kerry Ligtenberg of the Atlanta Braves and Denny Neagle of the Cincinnati Reds.

When doctors from the University of Toronto performed magnetic resonance imaging (MRI) scans on the shoulders of 14 minor league pitchers in the Toronto Blue Jays baseball organization last year, they found evidence of musculoskeletal damage even though the pitchers had no symptoms. Interestingly, the MRIs showed damage in both the pitching arm and the nonpitching arm – perhaps because the players' rigorous training and weightlifting program taxes both arms. The MRIs revealed tendinitis is 23 of the 28 shoulders examined and cartilage abnormalities in 22.

"Tendinitis and other rotator cuff abnormalities, the beginnings of bone spurs, degeneration and tears of the cartilage are problems you don't typically see among the general public, but they're part of life for many pitchers," said radiologist Anthony T. Mascia, in summarizing his group's findings.

Throwing a baseball can put an enormous strain on the arm. The pitcher must not only accelerate his arm forward to propel the ball, but also decelerate it rapidly during the follow-through to keep his shoulder from dislocating. Two joints – the hinged elbow and the ball – and – socket shoulder – bear the brunt of the force. The most common injuries are to the muscles, tendons and ligaments that hold those joints together. Children whose bones are still growing are at extra risk. The strain of throwing can stress growth plates at the ends of their bones, and damage the cartilage that normally keeps the joint sliding smoothly.

Dynamic Motion
"Throwing is a total body effort," Shaffer said. "It's not just from the shoulder to the hand. It begins with a tremendous transfer of momentum and energy from the legs and the trunk to the shoulder."

If you doubt that, try throwing a ball hard from a sitting position.

There are three main parts to the pitching motion: the windup or cocking phase, when the elbow reaches back behind the head; the acceleration phase, when the arm snaps forward; and the follow-through, after the ball is released. Each puts an abnormal stress on the elbow and shoulder.

"Pitching is one of the most dynamic motions in all sports," said Gill, of Massachusetts General Hospital. The whole forward pitching motion takes place in about a tenth of a second, he said, from the time the ball is behind the body to the moment it leaves the pitcher's hand.

"Here's this arm accelerating the ball," Gill said. "All of a sudden the ball is gone, and you've got to stop the arm from slapping the body – or coming off." He estimated the force at essentially the same as the pitcher's body weight: "That's like a 180-pound weight trying to pull your arm off."

Keeping the arm attached is the collaborative job of ligaments, which bind bones to bones; tendons, which attach muscles to bones; and muscles – particularly the rotator cuff, which stabilizes the shoulder and allows a person to raise and rotate the arm.

Gill and researchers from the Steadman-Hawkins Sports Medicine Clinic in Vail, Colo., studied 40 pitchers from eight major league baseball teams during spring training last year. The pitchers were videotaped from three camera angles to capture the pitching motion, breaking it down into 160 frames per pitch. Researchers studied each player's range of motion, stride length, arm angle and body rotation to see which movements were most likely to lead to injury.

The biggest risk of injury came when the pitcher's arm reached back too far, the elbow was too close to the body or the arm lagged behind the body as the ball was released.

The arm tends to lag farther and farther behind the rest of the body as the pitcher tires. That puts more and more stress on the elbow and shoulder, said Gill, who reported the findings to the American Academy of Orthopaedic Surgeons in February.

The shoulder is most vulnerable just before and just after the ball is released. At that point the arm is snapping forward so rapidly that it's a blur to the naked eye. If it were to keep moving at that speed, Gill calculated, it would whirl around (like a pinwheel or the spoke of a bicycle wheel) more than 20 times a second.

It doesn't, of course. But to keep the arm from pinwheeling or dislocating, the pitcher must rapidly decelerate it during the follow-through after every pitch. That strains the muscles, tendons and ligaments further.

More Than a Ball-and-Socket
Most people think of the shoulder as the ball-and-socket joint at the top of the arm. Sports medicine specialists like Rice see it as a complex of muscles, ligaments and bones reaching all the way from the collarbone to the upper arm and even connecting to the spinal column and the rib cage.

"It's a whole series of joints that must work in harmony for your arm to work right," Rice said.

Unlike the knee or the hip, the shoulder lacks bony stability and is held together mainly by muscles. The basic joint is where the round knob of the humerus bone fits against a socket called the glenoid cavity. But it's not a snug ball-and-socket like the hip. It's much less stable.

"More like a seal balancing a ball on its nose," Rice said. Others have compared the humerus to a golf ball and the glenoid to a tee. What's more, the tee is tipped sideways, so that gravity constantly threatens to pull the humerus out of its socket.

"It's not a stable joint," Rice said. "It's like a bunch of marionette strings trying to hold the puppet together. When the ball leaves your arm, it's your muscles that contract to pull your arm back and keep it from flying off."

When athletes say, "I threw my arm out," he noted, that is "absolutely an accurate description" of their injury.

"The message is: When you're throwing a ball and you feel any soreness, you stop," Rice said. "Because the next throw you make may be the one that causes permanent damage. You're not going to have the strength to be able to slow your arm down.

"You're going to overdo it. Things [in your arm] are going to move farther than they are supposed to, and things are going to rip."

Sources: Orthopedic surgeons Benjamin S. Shaffer and Robert P. Nirschl